Novel Properties of a Restriction Endonuclease Isolated from Haemophilus parahaemolyticus

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 73; no. 2; pp. 293 - 297
• Main Authors: Kleid, Dennis, Humayun, Zafri, Jeffrey, Andrea, Ptashne, Mark
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01.02.1976; National Acad Sciences
• Subjects: Base Sequence; Biochemistry; Chemical bases; Coliphages - analysis; DNA; DNA Restriction Enzymes - metabolism; DNA, Viral - analysis; DNA, Viral - metabolism; Endonucleases - metabolism; Enzymes; Gels; Genes, Regulator; Genetic mutation; Haemophilus - enzymology; Methylation; Molecules; Mutation; Operon; Purines; RNA; Structure-Activity Relationship
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.73.2.293

The sequences in λ DNA in and around six sites cut by Hph, a restriction enzyme isolated from Haemophilus parahaemolyticus, are compared. The enzyme produces a staggered cut around an AT or TA base pair, but the sequences immediately surrounding the cleavage sites bear no obvious relation to one another. Eight (in some cases nine) base pairs to one side of each cleavage site is the common sequence$ \smallmatrix \text{TCACC} \\ \text{TGTGG} \endsmallmatrix $. Two lines of evidence indicate that these bases constitute part or all of the Hph recognition site. First, mutations in this sequence prevent Hph cutting. Second, dimethylsulfate-mediated methylation of Gs and As in this site prevent cutting, whereas methylation of purines in the region between this sequence and the cleavage sites has no such effect. There is discernible 2-fold rotational symmetry neither in the common sequence nor around the cleavage sites.